Question: What are the historical ethnical group that starts with the letter 'x'
Paraphrase: What are the chronicled ethnical gather that begins with the letter 'x'
SPARQL (Wikidata): SELECT DISTINCT ?sbj ?sbj_label WHERE { ?sbj wdt:P31 wd:Q4204501 . ?sbj rdfs:label ?sbj_label . FILTER(STRSTARTS(lcase(?sbj_label), 'x')) . FILTER (lang(?sbj_label) = 'en') } LIMIT 25 
Answer: Xiongnu, Xiongnu, Xueyantuo, Xueyantuo